chore: import upstream snapshot with attribution

contributing/samples/workflows/node_as_tool/README.md

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+# Node as Tool
+
+## Overview
+
+Demonstrates wrapping both a regular ADK `Node` (using the `@node` decorator) and a `Workflow` as tools that can be automatically called by a parent `Agent`.
+
+In this sample:
+
+1. The parent agent receives an inquiry about a customer's discount.
+1. It invokes `customer_lookup_workflow` (a `Workflow` wrapped as a tool) to retrieve customer status.
+1. It then invokes `calculate_discount` (a regular `Node` wrapped as a tool) using the retrieved status.
+
+## Sample Inputs
+
+- `What discount does customer c123 get?`
+
+  *The parent agent first invokes `customer_lookup_workflow` to verify status, then invokes `calculate_discount` to determine the discount percentage, and summarizes the results.*
+
+## Agent Topology Graph
+
+```mermaid
+graph TD
+    customer_service_agent[customer_service_agent] -->|calls| customer_lookup_workflow(customer_lookup_workflow)
+    customer_service_agent -->|calls| calculate_discount(calculate_discount)
+```
+
+## How To
+
+To expose an existing `Node` or `Workflow` as a tool callable by an `Agent`:
+
+1. Define your `Node` (or `@node`) or `Workflow` and assign both an `input_schema` and a `description`.
+1. Pass the node/workflow directly into your parent agent's `tools` list: `Agent(..., tools=[my_node, my_workflow])`.
+
+## Related Guides
+
+- [Workflows](../../../../docs/guides/workflows/workflows.md) - Explains building complex multi-step graphs.

contributing/samples/workflows/node_as_tool/agent.py

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+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import annotations
+
+from typing import Generator
+
+from google.adk import Agent
+from google.adk import Event
+from google.adk import Workflow
+from google.adk.workflow import node
+from pydantic import BaseModel
+from pydantic import Field
+
+
+# 1. Define schemas
+class CustomerLookupArgs(BaseModel):
+  user_id: str = Field(description="The customer's unique identifier.")
+
+
+# 2. Define a regular Node using the @node decorator.
+# This Node is wrapped as a NodeTool automatically by the Agent.
+# As a NodeTool, it has the ability to yield intermediate Events during execution.
+@node
+def calculate_discount(tier: str, ctx) -> Generator[Event | str, None, None]:
+  """Calculates the discount percentage based on customer tier.
+
+  Args:
+    tier: The customer's membership tier (e.g., VIP, Standard).
+  """
+  yield Event(message=f"Checking discount rules for tier '{tier}'...")
+  discount = "20% off" if "VIP" in tier else "5% off"
+  yield discount
+
+
+# 3. Define a Workflow.
+# This Workflow is wrapped as a NodeTool automatically by the Agent.
+def lookup_customer_data(node_input: CustomerLookupArgs, ctx) -> dict[str, str]:
+  return {"user_id": node_input.user_id, "tier": "Verified VIP Member"}
+
+
+customer_lookup_workflow = Workflow(
+    name="customer_lookup_workflow",
+    description="Looks up customer status and tier by user_id.",
+    input_schema=CustomerLookupArgs,
+    edges=[
+        ("START", lookup_customer_data),
+    ],
+)
+
+
+# 4. Define the Agent that uses both Node and Workflow as tools.
+root_agent = Agent(
+    name="customer_service_agent",
+    instruction="""
+    You are a customer service assistant.
+    1. First, call `customer_lookup_workflow` using the user_id to get their membership tier.
+    2. Then, call `calculate_discount` node with that tier to find out what discount they get.
+    Summarize these details for the customer.
+    """,
+    tools=[customer_lookup_workflow, calculate_discount],
+)

contributing/samples/workflows/node_as_tool/tests/go.json

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+{
+  "appName": "node_as_tool",
+  "events": [
+    {
+      "author": "user",
+      "content": {
+        "parts": [
+          {
+            "text": "What discount does customer c123 get?"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-1",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": ""
+      }
+    },
+    {
+      "author": "customer_service_agent",
+      "content": {
+        "parts": [
+          {
+            "functionCall": {
+              "args": {
+                "user_id": "c123"
+              },
+              "id": "fc-1",
+              "name": "customer_lookup_workflow"
+            }
+          }
+        ],
+        "role": "model"
+      },
+      "id": "e-2",
+      "invocationId": "i-1",
+      "longRunningToolIds": [
+        "fc-1"
+      ],
+      "nodeInfo": {
+        "path": "customer_service_agent@1"
+      }
+    },
+    {
+      "author": "customer_lookup_workflow",
+      "branch": "customer_lookup_workflow@fc-1",
+      "id": "e-3",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "outputFor": [
+          "customer_lookup_workflow@1/lookup_customer_data@1",
+          "customer_lookup_workflow@1"
+        ],
+        "path": "customer_lookup_workflow@1/lookup_customer_data@1"
+      },
+      "output": {
+        "tier": "Verified VIP Member",
+        "user_id": "c123"
+      }
+    },
+    {
+      "author": "customer_service_agent",
+      "content": {
+        "parts": [
+          {
+            "functionResponse": {
+              "id": "fc-1",
+              "name": "customer_lookup_workflow",
+              "response": {
+                "tier": "Verified VIP Member",
+                "user_id": "c123"
+              }
+            }
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-4",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "customer_service_agent@1"
+      }
+    },
+    {
+      "author": "customer_service_agent",
+      "content": {
+        "parts": [
+          {
+            "functionCall": {
+              "args": {
+                "tier": "Verified VIP Member"
+              },
+              "id": "fc-2",
+              "name": "calculate_discount"
+            }
+          }
+        ],
+        "role": "model"
+      },
+      "id": "e-5",
+      "invocationId": "i-1",
+      "longRunningToolIds": [
+        "fc-2"
+      ],
+      "nodeInfo": {
+        "path": "customer_service_agent@1"
+      }
+    },
+
+    {
+      "author": "calculate_discount",
+      "branch": "calculate_discount@fc-2",
+      "content": {
+        "parts": [
+          {
+            "text": "Checking discount rules for tier 'Verified VIP Member'..."
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-6",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "calculate_discount@1"
+      }
+    },
+    {
+      "author": "calculate_discount",
+      "branch": "calculate_discount@fc-2",
+      "id": "e-7",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "outputFor": [
+          "calculate_discount@1"
+        ],
+        "path": "calculate_discount@1"
+      },
+      "output": "20% off"
+    },
+    {
+      "author": "customer_service_agent",
+      "content": {
+        "parts": [
+          {
+            "functionResponse": {
+              "id": "fc-2",
+              "name": "calculate_discount",
+              "response": {
+                "result": "20% off"
+              }
+            }
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-8",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "customer_service_agent@1"
+      }
+    },
+    {
+      "author": "customer_service_agent",
+      "content": {
+        "parts": [
+          {
+            "text": "Customer c123 is a Verified VIP Member and gets a 20% discount."
+          }
+        ],
+        "role": "model"
+      },
+      "id": "e-9",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "customer_service_agent@1"
+      }
+    }
+  ],
+  "id": "12345678-1234-1234-1234-123456789abc",
+  "userId": "user"
+}